...but more and more, over time, this is part of how we live now". Maddow shows us what the American history of mass gun violence looks like.

Since the first mass shooting in 1949, the increase in mass shootings resulting in the death of at least 12 hours excluding the gunman has kept apace. Of the 12 deadliest shootings in American history, half have taken place since 2007. In 2012 alone, there was two shootings resulting in a combined death toll of 39. Professor at the University of Maryland, Charles Catania says that this is "scariest data he had ever charted".